Apparatus for registering objects of revolution for printing

ABSTRACT

An apparatus for obtaining accurate registration of objects of revolution allowing multicolor printing of such objects by a screen printing apparatus, including a chuck for centering and mounting such objects, and a motor driven pulley and belt system to rotate the chuck and the object to a designated reference position prior to printing in which the pulley associated with the chuck is generally cylindrical in configuration, having a smooth, even surface which comes in contact with only a portion of the belt driving it to thereby reduce the frictional forces between the belt and the pulley and permit the pulley and belt to move relative to one another for printing, once the desired reference position has been obtained.

United States Patent 1191 Derrickson APPARATUS FOR REGISTERING OBJECTS OF REVOLUTION FOR PRINTING [75] Inventor: Charles H. Derrickson, Chicago, Ill.

[73] Assignee: American Screen Printing Equipment Company, Chicago, Ill.

22 Filed: Feb. 25, 1974 211 App]. No.: 445,221

101/123, 124, 126, 129, 115; 64/30 R, 30 E, 19, 28 R; 74/203, 219, 216.5, 230.7, 231 R, 230.5, 230.05, 229, 230.01

{56] References Cited UNITED STATES PATENTS 2,882,818 4/1959 Vowles 101/126 Homier et al 74/2165 X 1 1 Aug. 5, 1975 3,538,845 Peck et al. 101/126 X 1 5 7 1 ABSTRACT An apparatus for obtaining accurate registration of objects of revolution allowing multicolor printing of such objects by a screen printing apparatus, including a chuck for centering and mounting such objects, and a motor driven pulley and belt system to rotate the chuck and the object to a designated reference position prior to printing in which the pulley associated with the chuck is generally cylindrical in configuration, having a smooth, even surface which comes in contact with only a portion of the belt driving it to thereby reduce the frictional forces between the belt and the pulley and permit the pulley and belt to move relative to one another for printing, once the desired reference position has been obtained.

8 Claims, 6 Drawing Figures PATENTEU AUG 51975 SHEET PATENTEU M18 5 m5 SHEET 1 APPARATUS FOR REGISTERING OBJECTS OF REVOLUTION FOR PRINTING BACKGROUND OF THE INVENTION This invention relates to apparatus for registering objects of revolution prior to printing and in particular, to such a registration apparatus adapted for use with a screen printing machine.

Screen printing is widely used for printing objects of revolution, such as bottles, cans, cones, and the like. Various types of screen printers are available to accomplish such printing, and many, such as that shown in US. Pat. No. 3,090,300, involve a chuck which is mounted for free movement on a shaft extending outwardly from the printer, a screen which is movable laterally relative to the shaft, and a squeegee which is movable relative to the screen and the shaft. During the printing cycle, these elements are moved in timed relationship to one another, the object ordinarily being rotated, while the screen is moved across its surface.

In order to print more than one color on an object, however, it is necessary to begin at precisely the same point on the object for each color so that the colors match up or register. Therefore, the object itself must be registered with the chuck relative to the screen to avoid overlapping, smearing and a generally sloppy finished appearance. This registration has been attempted with a complex mechanical linkage including chains and gears or belts and pulleys driven by a motor mounted on the press to rotate the chuck and object angularly until a desired reference position is reached. This reference position is normally determined by an indented or raised ramp formed directly on the object which is engaged by a pin connected to the outward shaft on the printer. Since the chuck and object are often rotated at speeds of up to 500 r.p.m., a clutch placed in this mechanical linkage is disengaged when the pin engages the ramp to permit the chuck and held object to be moved by the press relative to the screen, and to avoid having the bottom of the object torn apart by the high torques exerted when the pin engages the rotating object. The complex interaction of multiple mechanical parts, however, has presented problems of mechanical breakdown and high manufacturing cost with this mechanism. Moreover, there is a definite time lag between the engagement of the object by the registering pin and the disengagement of the clutch, subjecting the object to stresses which, particularly in highdensity glass and plastic, cause breakage. Finally, where belts have been used in these previous registration systems, the frictional forces and torques exerted have caused rapid deterioration and breakage of these belts, necessitating the time and expense of constant replacement.

SUMMARY OF THE INVENTION The present invention involves an apparatus for accurately registering an object of revolution for multicolor screen printing which is mechanically simple and reliable in operation, reduces stresses on such objects and wear on parts and is inexpensive to manufacture. This invention overcomes the disadvantages of the prior art and accomplishes these objects by means of a multiple pulley and belt system which may be adjustably mounted on a screen printing press and acts to drive a chuck holding the object to be printed in an angular manner to a designated reference position,

whereupon the pulley structure continues to move but allows the chuck and object to be moved relative thereto by the printing press during printing. This apparatus includes a first pulley mounted for rotation about the same shaft as the chuck, which always moves in associated relationship with the chuck, and a second pulley mounted on a parallel but spaced axis extending outwardly from the press. The first pulley is connected to the second pulley by a first drive belt, and the second pulley is connected by a second drive belt to a drive motor mounted on the press. In this manner. the drive motor, upon actuation, will impart a rotation to the chuck and the object which will continue until a spring biased pin mounted on the end of the shaft supporting the chuck engages a stop formed on the object to thereby connect the object to the shaft for rotation relative to the screen during a printing cycle.

The first pulley adjacent and rotatable with the chuck is purposely formed in a square, i.e. generally cylindrical, configuration, having a smooth metal surface with a relatively low coefficient of friction. The surface of this pulley contacts the bottom, flat portion of a conventional V-shaped belt with a sufficient frictional force to allow the belt to turn the first pulley and chuck to the designated reference position. However, when the pin stops the chuck and object from further rotational movement relative to the shaft, this frictional force created between the belt and the first pulley will not be sufficient to rotate the shaft and the chuck, and the belt will slip on the squared pulley surface relative to the chuck and object. The press is then actuated so that the screen engages the shaft and rotates the shaft and the pin engaged object in an opposite direction for printing.

The unique construction of and relationship between the first pulley and the first belt completely eliminates the need for the complex gear and clutch arrangements of the prior art, while accomplishing precise registration and a significant reduction of undesirable stresses. The cost saving in manufacturing this invention is substantial over that of the prior art, and the likelihood of mechanical breakdown and wear is greatly reduced.

Accordingly, it is an object of the present invention to provide an apparatus for registering objects of revolution relative to a means for printing such objects which is simple in operation and construction and inexpensive in cost to manufacture.

It is a further object of this invention to provide an apparatus for registering objects of revolution which has few moving parts and allows continuous operation of the registration apparatus during a printing cycle without affecting the printing of such objects.

It is one more object of the invention to provide an apparatus for registering an object of revolution for printing by a screen printing press which uses a minimized area of contact between a pulley and a belt to reduce frictional forces and stresses during a printing cycle.

It is another object of the present invention to pro vide an apparatus for registering objects of revolution relative to a screen printing press having a pulley and belt system in which the pulley associated with the chuck holding the object to be printed is formed in such a manner that frictional forces between the belt and that pulley are substantially reduced, thereby allowing relative movement between the belt and that pulley after registration of the object and reducing stresses on the object during registration.

These and other objects of the present invention will become more apparent through the following description taken in connection with the drawings, wherein:

FIG. I is a perspective view of the registration apparatus of this invention shown mounted on a press designed for screen printing objects of revolution;

FIG. 2 is a slightly enlarged left hand elevational view of the registration apparatus shown in FIG. I, adjusted to an inward position;

FIG. 3 is a left hand elevational view of the registration apparatus shown in FIG. I, adjusted to an outward position;

FIG. 4 is a cross-sectional view of the second pulley and belt means of the registration apparatus of this invention, taken generally along line 44 in FIG. 3;

FIG. 5 is a slightly enlarged cross-sectional view showing the first pulley and first belt of the registration apparatus of the present invention and its means for connection to the screen printing press; and,

FIG. 6 is a cross-sectional view taken generally along line 66 in FIG. 5.

DESCRIPTION OF THE INVENTION Referring now to the drawings, and, in particular, to FIG. 1, the apparatus for registering objects of revolution for printing is shown in general at 10. This registration apparatus 10 is shown mounted on a commercially available screen printing press 12 which is convertible from fiat to round printing for use in printing cylinders, cones, and other objects of revolution. The registration apparatus 10 is adaptable for use with any shape object which may be printed on this press, including bottles, jars, cylindrical lighters, buckets, vases, coffee pots, and so on.

The screen printing press 12 includes a squeegee and screen mount 14 which moves laterally across the press on press shafts 16. The squeegee and the screen, which are not shown in order to facilitate illustration of the registration apparatus, are movable relative to one another and to the object to be printed. A toothed rack 18 is mounted at the front of the press 12 and associated with mount I4 to engage and move gear 42, corresponding to the movement of the screen across the press, as will be explained below.

The registration apparatus 10 includes a drive motor 20 which may, because of the unique operation of the present invention, be run continuously, thereby conserving power, wasted starting and stopping time and excessive wear on the motor itself. Motor 20 includes a drive pulley 22 which rotates about a motor drive shaft. Immediately above drive motor 20 a second drive pulley assembly 23 is mounted on the press 12. Assembly 23 includes a second inside pulley 24 and a second outside pulley 25, both mounted on a hollow sleeve 26, having a key 27 formed along its length. Outside pulley 25 is mounted on the outer end of sleeve 26, and inside pulley 24 is mounted over key 27 to permit adjusting movement of the sleeve relative to the pulley 25. Rota tion of the sleeve 26 will rotate both pulleys correspondingly. I-Iollow sleeve 26 is securely mounted in a desired position on a second pulley shaft 28, which is mounted through a second pulley mount by an adjusting screw 3]. Sleeve 26 may be moved relative to pulley shaft 28 to move outside pulley 25 away from the printing press to permit printing of larger objects.

Inside pulley 24, however, should remain vertically aligned with drive pulley 22 so that effective transfer of torque through a second belt 32 connecting the inside pulley 24 and drive pulley 22 is obtained.

The second drive pulley assembly 23 is connected by a first belt 34 to a first drive pulley and chuck assembly 35. Assembly 35 includes a molded plastic chuck 36 at its outermost end, which is specially formed to hold and center the particular object to be printed. A lightweight chuck molded from nylon or the like is preferred, because of its low cost and inherent surface lubricity which reduces stresses on the object during registration. The chuck 36 is specially molded to the bottom or other desired dimension of the object which is to be printed. The chuck 36 shown in FIG. 5 is of varying cross-sectional diameters and is formed with an opening at each end. Into the narrower opening at the inward end of chuck 36 is inserted a reduced diameter portion 38 of a first pulley 37. Set screws 41 mounted in the inward end of the chuck 36 are moved to engage the portion 38 of the first pulley 37 so that the first pulley 37 and chuck 36 will always move together. The first pulley 37 and the chuck 36 are mounted for angular movement over a first shaft 39 by needle bearings (not shown) which allow them to rotate freely relative to this shaft. Shaft 39 is connected to gear 42 by hollow adapting sleeve 43 for angular movement about a central axis with gear 42. The position of shaft 39 may be adjusted relative to sleeve 43 by means of a sleeve screw 45, which engages a flat 40 formed in shaft 39. The first pulley 37 and chuck 36 may thereby be adjusted outwardly relative to the printing press I2 in the same manner and to the same distance as second outside pulley 25. Thus, the outside pulley 25 and the first pulley 37 will always be aligned in the same plane so that the first belt 34 which connects the two pulleys will drive them in an efficient manner. The first pulley assembly 35 is mounted on the printing press 12 by means of a winged mounting collar 54 which is adjustably attached to the upwardly extending standards of a U-shaped mount 57 secured to the printing press I2. The slots in these standards permit vertical adjustment of the first pulley and chuck assembly so that objects of large diameter may be accurately registered and printed. A standard collar 56 engages shaft 39 to position the mounting collar adjacent the first pulley.

On the outward end of the first shaft 39 and within chuck 36 is mounted an outside plate 46 and an inside plate 47, as shown in FIG. 5. These two plates contain a registration pin 50 having an inward end disposed in a chamber 53. Pin 50 is outwardly biased toward the large opening 62 in the chuck by a spring 51, and plates 46 and 47 are joined by a plurality of bolts (not shown). These plates are not joined to the chuck or the first pulley but are formed with sufficient clearance between their outside diameters and the inside diameter of the chuck to allow relative rotational speeds of approximately 500 rpm. The use and general structure of the above-described registration pin and chuck are subject to a great many variations, depending on the shape of the object to be printed, and are known in the art. The present invention, however, obtains its advantages through a novel construction of first pulley 37 and its relationship to belt 34.

The larger diameter portion of the first pulley 37 which engages the first belt 34 is formed square, that is, in a cylindrical shape with a flat surface 48. This surface 48 is machined smooth to eliminate any ridges or burrs and thereby reduce its coefficient of friction. First and second belts 34 and 32 are commercially available V-belts," and drive pulley 22 and second outside pulley 25 have cross-sectional surfaces which conform to the shape of these belts, and are, in this respect, similar to previously used apparatus. When belt 34 is placed over first pulley 37, however, only the small parallel side of the trapezoid forming the belt contacts the smooth surface of the first pulley. The upwardly extending flanges of the pulley do not engage the belt. The limited contact provided by the design and manufacture of first pulley 37 will substantially reduce the frictional forces present in the prior art where the pulleys were formed to engage three'sides of the V- belt or were purposely formed with ridges over their outside surfaces to attempt to obtain high frictional forces between the belt and thepulley, which, it was thought, were necessary for proper registration. The unique structural relationship between the first pulley 37 and first belt 34 of this invention, however, has been found to still produce the angular speednecessary for fast registration, while at the same time being sensitive to finger pressure resistance and therefore not transferring the excessive torque normally incident to high speed to the object upon registration. The registration apparatus is completed by an idler pulley 64 which is mounted by tension adjusting assembly 66 on the printing press 12. This pulley allows adjustment in the tension in the first belt 34 according to the requirements of the printing process so that accurate registration and desired slipping of the belt 34 relative to the first pulley 37 is obtained, as will be described below.

In operation of the registration apparatus 10 during a printing cycle, the object 58 which is to be printed is inserted into the large opening 62 in the chuck. Each object 58 has an inwardly extending arcuate ramp 60, as shown in FIGS. 5 and 6 or, alternately, a raised portion on its bottom which acts as a stop to engage the registration pin 50, as is known inthe art. The ramp 60 and pin 50 are aligned so that the pin 50 enters and moves along ramp 60 as the chuck 36 and object are rotated relative to the temporarily stationary pin 50 prior to printing. The chuck and object are rotated by the attached first pulley 37 and the remainder of the pulley and belt system which is driven by the drive motor 20. The turning speed of the chuck may reach approximately 500 r.p.m., and the forces ordinarily exerted by the end of the ramp engaging the pin can be readily appreciated. For example, in the prior art design, because of the time lag between actual engagement of the object and the registration pin and the operation of the clutch disengaging the first belt driving the first pulley and chuck, the first belt would continue to attempt to drive the chuck and object counterclockwise, against the resistance of the shaft 39, creating tremendous undesirable stresses in the object which often caused cracking or fracture, particularly in high density glass and plastics. The great frictional force between the first belt and first pulley not only increased these torques and stresses but also resulted in excessive wear on the belt, requiring its constant replacement. in the present invention, however, when the pin engages the stop 68 on the object, the first belt and first pulley, be cause of the construction of the first pulley and the relationship of their surfaces which produces low frictional forces, immediately slip relative to one another.

Thus, the first belt exerts no further rotating force on the pulley, and stresses in the object are tremendously reduced. In the present invention, a frictional force sufficient to drive the chuck and object but insufficient to overcome finger pressure against the chuck or the pulley has been found suitable for purposes of registration.

Once the pin has engaged the stop 68 formed in the object, the object is brought to its precise, designated reference position for printing. Since the stop 68 is actually formed in the object, engagement of the registration pin and this stop will always result in precise registration for each color to be printed. Therefore, when the rack 18 engages the gear 42, as the screen moves over and toward the surface of the object to be printed. the first shaft 39 and the now engaged object will be rotated in an opposite direction to registration, normally clockwise. The object will rotate relative to the screen and also relative to the direction of movement of the first belt 34, which continues to slip on the smooth surface of the first pulley 37.

The materials from which this invention are manufactured are all, with the exception of the chuck and the belt, of steel or steel alloys and are commercially available. The chuck, pulley and all other parts which rotate relative to one another are normally mounted on the shaft through needle bearings and are separated by thrust bearings because of axial forces which must be absorbed in assembling the apparatus.

Upon consideration of the foregoing, it will become obvious to the those skilled in the art that various modifications may be made without departing from the invention embodied herein. Therefore, only such limitations should be imposed as are indicated by the spirit and scope of the appended claims.

I claim:

1. An apparatus for accurately registering objects of revolution relative to a screen printing press having a screen assembly and a squeegee assembly movable relative to one another to assure that the printing of each object will always be initiated from a designated refer ence position on that object, including a centering and positioning chuck mounted on a shaft extending outwardly from said screen printing press, said object to be printed being positioned on said chuck, said chuck and said object being angularly movable about a central axis of said shaft relative to said shaft to a designated reference position by drive means operatively connected to said chuck, said drive means including a first pulley associated with said chuck, said first pulley having a generally cylindrical, smooth exterior surface, and a second pulley rotatable about a central axis thereof relative to said printing press, said second pulley being operatively connected to said first pulley by a first belt, and said second pulley being operatively connected to a drive pulley by a second belt, said drive pulley being rotatable to cause said second pulley to be rotated about said central axis thereof, thereby imparting angular movement to said first pulley through said first belt, such that said first pulley and said chuck and said object positioned thereon are moved angularly in a selected direction relative to said shaft to said designated reference position, said shaft having registration means mounted thereon to engage said object and stop rotation of said first pulley and said object in said designated reference position, said smooth surface of said first pulley being in intimate, contacting relationship with a portion of an exterior surface of said first belt such that as the angular movement of said first pulley and said object is stopped by the engagement of said registration means with said object in said designated reference position, the limited frictional forces created between the engaging surfaces of said first pulley and said first belt permit continued movement of said first belt in said selected angular direction while allowing said chuck and said object to be moved with said shaft in an opposite angular direction for printing.

2. The apparatus of claim I wherein said first pulley means is formed in a generally cylindrical configuration such that it has a minimal cylindrical surface area available to engage said first belt to thereby allow said first belt to slip relative to said first pulley to permit oppositely directed movement of said first belt and said first pulley means during a printing cycle after said object of revolution has been moved angularly to said desired reference position.

3. The apparatus of claim 1 wherein said first pulley has a smooth, clean, generally cylindrical surface which only engages a portion of the exterior surface of said first belt connecting said first pulley to said second pulley to thereby reduce the frictional forces between said pulley surface and said belt to permit them to be moved relative to one another while remaining in constant engagement without exerting undesirable rotational forces on said object.

4. The apparatus of claim 3 wherein said smooth, generally cylindrical surface of said first pulley contacts a flat portion of a first belt means to thereby reduce the friction therebetween and permit said first belt means to continue to move in one direction while said chuck and said first pulley are rotated in an opposite direction with said object by said means for printing.

5. The apparatus of claim 1 wherein said first belt is placed in intimate contacting relationship with only that portion of the surface area of said first pulley that will create sufficient friction therebetween to allow said first pulley to be rapidly moved by said first belt to said designated reference position of said object relative to said shaft, but which will quickly permit opposite movement of said first pulley relative to said first belt after said reference position has been attained.

6. The apparatus of claim 1 wherein said registration means is an outwardly biased pin mounted on said shaft, which engages stop means mounted on said object as said object is rotated with said chuck relative to said shaft to immediately stop angular movement of said first pulley by said first belt.

7. In a printing press particularly adapted for printing a plurality of colors on objects of revolution, said press including printing means movable relative to said object during a printing cycle, a chuck mounted on said printing press for receiving an object to be printed, a shaft mounted on said printing press, said object being rotatable about a central axis of said shaft relative to said printing means during a printing cycle. a first pulley associated with said chuck for angular movement therewith. and a second pulley rotatably mounted on said printing press, said first pulley being connected to said second pulley by a first belt, and said second pulley being connected to a drive means by a second belt, said shaft having a registration pin associated therewith, said pin engaging a stop means formed on said object, when said chuck and said object have been angularly moved to a designated reference position to obtain precise registration of said object relative to said printing means to assure accurate printing of multiple colors on said object, the improvement including said first pulley having a smooth, generally cylindrical exterior surface which frictionally engages a minimum surface area of said first belt to create a limited frictional force between said belt and said surface of said pulley sufficient to allow said pulley, said chuck means and said object to be angularly moved toward said designated reference position, said frictional force thereby created being insufficient to move said object subsequent to the engaging of said stop means by said registration pin at said designated reference point, despite allowing said first belt to continue moving angularly in a direction opposite that in which said first pulley, said chuck and said object are moved by said printing means through said shaft.

8. The improvement set forth in claim 7 wherein said first pulley connected to said chuck means has a relatively smooth, even surface which contacts only a fiat portion of said first belt to reduce the friction therebetween and permit said belt to continue to move in one direction while said chuck and said pulley are rotated oppositely on said shaft after registration of said object has been achieved.

10 i IF i 

1. An apparatus for accurately registering objects of revolution relative to a screen printing press having a screen assembly and a squeegee assembly movable relative to one another to assure that the printing of each object will always be initiated from a designated reference position on that object, including a centering and positioning chuck mounted on a shaft extending outwardly from said screen printing press, said object to be printed being positioned on said chuck, said chuck and said object being angularly movable about a central axis of said shaft relative to said shaft to a designated reference position by drive means operatively connected to said chuck, said drive means including a first pulley associated with said chuck, said first pulley having a generally cylindrical, smooth exterior surface, and a second pulley rotatable about a central axis thereof relative to said printing press, said second pulley being operatively connected to said first pulley by a first belt, and said second pulley being operatively connected to a drive pulley by a second belt, said drive pulley being rotatable to cause said second pulley to be rotated about said central axis thereof, thereby imparting angular movement to said first pulley through said first belt, such that said first pulley and said chuck and said object positioned thereon are moved angularly in a selected direction relative to said shaft to said designated reference position, said shaft having registration means mounted thereon to engage said object and stop rotation of said first pulley and said object in said designated reference position, said smooth surface of said first pulley being in intimate, contacting relationship with a portion of an exterior surface of said first belt such that as the angular movement of said first pulley and said object is stopped by the engagement of said registration means with said object in said designated reference position, the limited frictional forces created between the engaging surfaces of said first pulley and said first belt permit continued movement of said first belt in said selected angular direction while allowing said chuck and said object to be moved with said shaft in an opposite angular direction for printing.
 2. The apparatus of claim 1 wherein said first pulley means is formed in a generally cylindrical configuration such that it has a minimal cylindrical surface area available to engage said first belt to thereby allow said first belt to slip relative to said first pulley to permit oppositely directed movement of said first belt and said first pulley means during a printing cycle after said object of revolution has been moved angularly to said desired reference position.
 3. The apparatus of claim 1 wherein said first pulley has a smooth, clean, generally cylindrical surface which only engages a portion of the exterior surface of said first belt connecting said first pulley to said second pulley to thereby reduce the frictional forces between said pulley surface and said belt to permit them to be moved relative to one another while remaining in constant engagement without exerting undesirable rotational forces on said object.
 4. The apparatus of claim 3 wherein said smooth, generally cylindrical surface of said first pulley contacts a flat portion of a first belt means to therebY reduce the friction therebetween and permit said first belt means to continue to move in one direction while said chuck and said first pulley are rotated in an opposite direction with said object by said means for printing.
 5. The apparatus of claim 1 wherein said first belt is placed in intimate contacting relationship with only that portion of the surface area of said first pulley that will create sufficient friction therebetween to allow said first pulley to be rapidly moved by said first belt to said designated reference position of said object relative to said shaft, but which will quickly permit opposite movement of said first pulley relative to said first belt after said reference position has been attained.
 6. The apparatus of claim 1 wherein said registration means is an outwardly biased pin mounted on said shaft, which engages stop means mounted on said object as said object is rotated with said chuck relative to said shaft to immediately stop angular movement of said first pulley by said first belt.
 7. In a printing press particularly adapted for printing a plurality of colors on objects of revolution, said press including printing means movable relative to said object during a printing cycle, a chuck mounted on said printing press for receiving an object to be printed, a shaft mounted on said printing press, said object being rotatable about a central axis of said shaft relative to said printing means during a printing cycle, a first pulley associated with said chuck for angular movement therewith, and a second pulley rotatably mounted on said printing press, said first pulley being connected to said second pulley by a first belt, and said second pulley being connected to a drive means by a second belt, said shaft having a registration pin associated therewith, said pin engaging a stop means formed on said object, when said chuck and said object have been angularly moved to a designated reference position to obtain precise registration of said object relative to said printing means to assure accurate printing of multiple colors on said object, the improvement including said first pulley having a smooth, generally cylindrical exterior surface which frictionally engages a minimum surface area of said first belt to create a limited frictional force between said belt and said surface of said pulley sufficient to allow said pulley, said chuck means and said object to be angularly moved toward said designated reference position, said frictional force thereby created being insufficient to move said object subsequent to the engaging of said stop means by said registration pin at said designated reference point, despite allowing said first belt to continue moving angularly in a direction opposite that in which said first pulley, said chuck and said object are moved by said printing means through said shaft.
 8. The improvement set forth in claim 7 wherein said first pulley connected to said chuck means has a relatively smooth, even surface which contacts only a flat portion of said first belt to reduce the friction therebetween and permit said belt to continue to move in one direction while said chuck and said pulley are rotated oppositely on said shaft after registration of said object has been achieved. 